The composite member relates to a composite member separating method, thin film manufacturing method, and composite member separating apparatus.
Various manufacturing methods have been proposed to form a thin film of an insulator (dielectric material), conductor, semiconductor, or magnetic material, including a method of separating a composite member constructed by at least two kinds of layers having different materials or structures to form a thin film.
An SOI layer will be exemplified below as a thin film to help understand these methods.
Japanese Patent Laid-Open No. 7-302889 and U.S. Pat. No. 5,856,229 disclose a method of bonding a first member having a porous layer formed on a single-crystal Si substrate and a single-crystal non-porous layer thereon to a second member via an insulating layer to form a composite member, and separating the composite member into two parts at the porous layer acting as a separation layer, thereby transferring the single-crystal non-porous layer to the second member. This technique is excellent because the film thickness uniformity of the SOI layer is high, the crystal defect density in the SOI layer can be reduced, the surface planarity of the SOI layer is good, and an SOI substrate having an SOI layer having a thickness of about several ten nm to ten xcexcm can be manufactured.
Additionally, this method is advantageous because the single-crystal Si substrate can be separated from the second member without breaking most part of the single-crystal Si substrate, and the separated Si substrate can be reused.
To separate the bonded substrate stack into two substrates, for example, the two substrates are pulled in opposite directions while applying a force in a direction perpendicular to the bonding interface, a shearing force is applied parallel to the bonding interface (for example, the two substrates are moved in opposite directions in a plane parallel to the bonding interface, or the two substrates are rotated in opposite directions while applying a force in the circumferential direction), a pressure is applied in a direction perpendicular to the bonding interface, a wave energy such as an ultrasonic wave is applied to the separation region, a peeling member (e.g., a sharp blade such as knife) is inserted into the separation region parallel to the bonding interface from the side surface side of the bonded substrate stack, the expansion energy of a substance filling the pores of the porous layer functioning as the separation region is used, the porous layer functioning as the separation region is thermally oxidized from the side surface of the bonded substrate stack to expand the volume of the porous layer and separate the substrates, or the porous layer functioning as the separation region is selectively etched from the side surface of the bonded substrate stack to separate the substrates.
Such a method is disclosed in U.S. Pat. No. 5,854,123, Japanese Patent Laid-Open No. 11-237884, 10-233352, or European Patent Laid-Open No. 0867917.
Japanese Patent Laid-Open No. 5-211128 and U.S. Pat. No. 5,374,564 disclose a method of forming a substrate by implanting ions of, e.g., hydrogen into a single-crystal Si substrate from its upper surface side to form an ion implantation layer acting as a separation layer in the substrate, where the concentration of the implanted ions is locally high, bonding the resultant substrate to another substrate, and heating the bonded substrate stack to separate it into two parts.
In the above-described separating methods, how to stabilize the position where a crack forms at the initial stage of separation is important.
For example, if a crack that formed at a portion except the separation layer grows toward the center of a substrate in separating a bonded substrate stack, a thin film as a prospective SOI layer breaks to lower the manufacturing yield of SOI substrates.
The present invention has been made in consideration of the above situation, and has as its first object to, e.g., improve the reproducibility of a crack generation position in a composite member such as a bonded substrate stack and suppress the amount of damage to the thin film at the end portion.
It is the second object of the present invention to appropriately separate a composite member at a separation layer such as a porous layer or ion implantation layer.
According to the first aspect of the present invention, there is provided a composite member separating method of separating a composite member formed by bonding a first member having a separation layer and a transfer layer on the separation layer to a second member, at a position different from a bonding interface between the first member and the second member, comprising the pre-separation step including the step of applying a force asymmetric with respect to the bonding interface to an end portion of the composite member to form, in the composite member, a crack that runs from a surface of the first member to the separation layer through the transfer layer, and the actual separation step including the step of growing the crack along the separation layer.
According to the second aspect of the present invention, there is provided a thin film manufacturing method comprising the step of bonding a first member having a separation layer and a transfer layer on the separation layer to a second member to form a composite member, and the separation step of separating the composite member at a position different from a bonding interface between the first member and the second member, wherein the separation step comprises the first step of applying a force asymmetric with respect to the bonding interface to an end portion of the composite member to form, in the composite member, a crack that runs from a surface of the first member to the separation layer through the transfer layer, and the second step of growing the crack along the separation layer.
According to the third aspect of the present invention, there is provided a composite member separating apparatus for separating a composite member formed by bonding a first member having a separation layer and a transfer layer on the separation layer to a second member, at a position different from a bonding interface between the first member and the second member, comprising a pre-separation mechanism for applying a force asymmetric with respect to the bonding interface to an end portion of the composite member to form, in the composite member, a crack that runs from a surface of the first member to the separation layer through the transfer layer, and an actual separation mechanism for growing the crack along the separation layer.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.